ALLEGRO_PIXEL_FORMAT

Pixel formats. Each pixel format specifies the exact size and bit layout of a pixel in memory. Components are specified from high bits to low bits, so for example a fully opaque red pixel in ARGB_8888 format is 0xFFFF0000.

Note:

The pixel format is independent of endianness. That is, in the above example you can always get the red component with

(pixel &0x00ff0000)>>16

But you can not rely on this code:

*(pixel +2)

It will return the red component on little endian systems, but the green component on big endian systems.

Also note that Allegro's naming is different from OpenGL naming here, where a format of GL_RGBA8 merely defines the component order and the exact layout including endianness treatment is specified separately. Usually GL_RGBA8 will correspond to ALLEGRO_PIXEL_ABGR_8888 though on little endian systems, so care must be taken (note the reversal of RGBA <-> ABGR).

The only exception to this ALLEGRO_PIXEL_FORMAT_ABGR_8888_LE which will always have the components as 4 bytes corresponding to red, green, blue and alpha, in this order, independent of the endianness.

ALLEGRO_PIXEL_FORMAT_ANY - Let the driver choose a format. This is the default format at program start.

ALLEGRO_PIXEL_FORMAT_ANY_NO_ALPHA - Let the driver choose a format without alpha.

ALLEGRO_PIXEL_FORMAT_ANY_WITH_ALPHA - Let the driver choose a format with alpha.

ALLEGRO_PIXEL_FORMAT_ABGR_8888_LE - Like the version without _LE, but the component order is guaranteed to be red, green, blue, alpha. This only makes a difference on big endian systems, on little endian it is just an alias.